I just thought people may be interested in this new Sony / Legacy webpage that lets users suggest and vote for reissues: http://legacyrecordings.uservoice.com
Currently the highest rated listings are both encouraging Legacy to release more SACDs, including original Quadraphonic mixes on the multi-channel layer:
You have a maximum of ten votes. You can vote anonymously, or sign up for a personalised account.
It costs one vote to make a new suggestion. But make sure it is something Legacy owns, and something not previously suggested (there's a search function at the top of the page).